Applications involving the diffusion of gas into liquid include the aeration/mixing of water and wastewater in basins, lagoons, ponds and other containment structures. In the aeration/mixing of wastewater, multiple diffuser modules have been used with considerable success. A typical system includes floating or submerged air laterals which receive air from a blower or fan and apply the air through flexible air lines extending to submerged diffuser modules which may be arranged in a grid or other configuration. The diffuser modules may be of various types, one of which is a construction having a header pipe supporting elongated diffuser pipes that extend from its opposite sides. The diffusers may be flexible membrane tube diffusers having flexible membranes sleeved over the diffuser pipes, flexible membrane disk diffusers mounted on the diffuser pipes, or any other suitable type of diffuser. The modules may be arranged in a grid pattern throughout the basin to provide thorough and uniform mixing/aeration of the waste water.
Although systems using diffuser modules of this type have been successful, they are not wholly without problems. Maintenance and repair of the diffusers can be particularly difficult because of their submerged location. The diffusers must either be maintained or repaired in place, or, more commonly, the entire module containing one or more worn or defective diffusers must be lifted to the surface using a large crane or other heavy equipment. In large installations, it may be difficult if not impossible for a crane to reach units in the center or near a remote side or end of the basin, even if the crane is equipped with a lengthy boom. The need for heavy ballast to hold the modules down in normal operation adds to the difficulty involved in raising and maintaining the modules.
After maintenance and repair operations have been completed, the module must be replaced in the basins, again requiring the use of a crane or other heavy equipment and again complicated by the heavy ballast. Replacing the module involves the risk of damage, particularly if the module is tilted appreciably or is otherwise handled improperly as it is being lowered in the basin. If one or more of the diffusers are damaged during replacement, additional repair work is necessary and additional downtime of the entire system may result.
Handling the modules in this fashion exerts considerable stress on the piping. Consequently, the module size has been restricted due to structural considerations. Even then, the piping can be easily broken or otherwise damaged during maintenance operations.